[dns-operations] Debugging Google Public DNS

[Roy Arends]

On Jun 3, 2013, at 3:58 PM, Stephane Bortzmeyer <bortzmeyer at nic.fr> wrote:

> Some instances of Google Public DNS cannot resolve ripe.net :
> 
> % dig @8.8.8.8 MX ripe.net
> 
> ; <<>> DiG 9.8.1-P1 <<>> @8.8.8.8 MX ripe.net
> ; (1 server found)
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: SERVFAIL, id: 6005
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0
> 
> ;; QUESTION SECTION:
> ;ripe.net.			IN	MX
> 
> ;; Query time: 3343 msec
> ;; SERVER: 8.8.8.8#53(8.8.8.8)
> ;; WHEN: Mon Jun  3 15:57:00 2013
> ;; MSG SIZE  rcvd: 26
> 
> But some can:
> 
> % dig @8.8.8.8 MX ripe.net      
> 
> ; <<>> DiG 9.8.4-rpz2+rl005.12-P1 <<>> @8.8.8.8 MX ripe.net
> ; (1 server found)
> ;; global options: +cmd
> ;; Got answer:
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 55124
> ;; flags: qr rd ra ad; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 1
> 
> ;; OPT PSEUDOSECTION:
> ; EDNS: version: 0, flags: do; udp: 512
> ;; QUESTION SECTION:
> ;ripe.net.			IN	MX
> 
> ;; ANSWER SECTION:
> ripe.net.		252	IN	MX	250 postlady.ripe.net.
> ripe.net.		252	IN	MX	200 postgirl.ripe.net.
> ripe.net.		252	IN	RRSIG	MX 5 2 300 20130703100234 20130603090234 61825 ripe.net. LA+iNlYx/wJPljhvQNQFVL1LisMjDnlNVVFoH/780HYcEIKFaJ5Wm4eD C9FPJQKfX14ZD2T9i7R3qGx6GvFaKqSXhLtWlH4NGM/T4UYhl61L25FL S6qiHDu20tJe4u2/xmmLuqBicj3kCmDuAk0j1Vc851/edBtqR+Kx1LXt HHM=
> 
> ;; Query time: 7 msec
> ;; SERVER: 8.8.8.8#53(8.8.8.8)
> ;; WHEN: Mon Jun  3 15:57:18 2013
> ;; MSG SIZE  rcvd: 255
> 
> Since Google Public DNS has apparently no NSID or version.bind,
> besides traceroute, what are the tricks to find the extent of the problem?

The problem is not google.

You're testing from two different locations: the different DiG versions show this. I guess the first instance is running from a network in some conference room in Amsterdam. Reason 1: we are in the same conference room :-) Reason 2: a traceroute from my shell account shows the exact same path.

Your queries have been capture by the local hotel network to maximise user experience :-)

To be complete, I've just tested all the instances of google public DNS' unicast resolver source addresses (for a list see: https://developers.google.com/speed/public-dns/faq ) from outside the hotel network and all return with the same, correct, data.

Hope this helps.

Roy

> 
> For the offending instance:
> 
> % traceroute 8.8.8.8
> traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets
> 1  192.168.48.1 (192.168.48.1)  0.972 ms  0.938 ms  1.858 ms
> 2  87.213.29.57 (87.213.29.57)  4.524 ms  4.516 ms  4.495 ms
> 3  ge-2-0-0-1334.ncr01asd2.versatel.net (217.16.40.97)  4.475 ms  4.456 ms  4.455 ms
> 4  xe-2-2-0-672.br04sara.versatel.net (212.53.22.82)  39.255 ms  39.279 ms  39.248 ms
> 5  core1.ams.net.google.com (195.69.144.247)  4.330 ms  4.321 ms  4.309 ms
> 6  209.85.248.118 (209.85.248.118)  5.070 ms  2.973 ms  3.758 ms
> 7  209.85.255.60 (209.85.255.60)  4.019 ms 209.85.255.72 (209.85.255.72)  5.081 ms  5.081 ms
> 8  216.239.49.30 (216.239.49.30)  33.150 ms 216.239.49.36 (216.239.49.36)  7.485 ms  8.902 ms
> 9  * * *
> 10  google-public-dns-a.google.com (8.8.8.8)  8.725 ms  8.775 ms  8.689 ms
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